1. Field of the Invention
This invention relates, generally, to clamps for sanitary fittings. More particularly, it relates to a clamp for clamping together two sanitary fittings with a force that is predetermined and which may be duplicated repeatedly.
2. Description of the Prior Art
Conventional sanitary clamps are typically made of stainless steel, a rigid plastic, or a combination of such materials. In a first well-known design, two semicircular parts are hingedly connected to one another at a first end and their free ends are secured to one another by a threaded stem and nut. In another well-known embodiment, the two semicircular sections are secured to one another by a flexible steel or plastic band that circumscribes them. A mechanism of the type commonly used on hose clamps pulls the semicircular parts toward one another by tightening the band via rotation of a worm gear that meshingly engages slots formed in the flexible band.
The primary drawback of the known clamps is that they include no means for applying an optimal amount of force. Accordingly, they are usually over-tightened. Over-tightening is particularly undesirable when a plastic fitting is used because the fitting may buckle. Such buckling can compromise the fluid tightness and the pressure resistance of the connection.
A closely related drawback is that the force applied by the known clamps is not repeatable. Thus, if a prior art clamp is tightened by an optimal force-providing amount, by luck, there is no means for repeating such optimal tightening the next time a clamp of the same structure is used.
There is a particular type of commercially available sanitary clamp that includes a torque indicator in a threaded closure nut that overcomes the over-tightening problem. However, this is a relatively expensive solution to the problem.
A conventional torque wrench may also be used to overcome the over-tightening problem. However, such wrenches are cumbersome and inconvenient to use.
Another drawback associated with sanitary fittings that are tightened with torque wrenches is that the installation is not tamper-evident. A torque wrench on a simple screw clamp, even if it is incorporated into the clamp, is easily opened. If the sanitary fitting is opened and tampered with and re-closed with a torque wrench, there is no evidence of such tampering
Moreover, the amount of tension applied to the clamp cannot be checked by visual inspection after the torque wrench has been removed.
What is needed is an inexpensive clamp that may be tightened repeatedly and consistently to an optimal tightness but that does not require an internal torque indicator in a threaded closure nut or use of a torque wrench.
There is also a need for a tamper-evident installation.
A need is also extant for an installation that provides a visual indication of whether or not a sanitary fitting has been properly tightened.
However, in view of the prior art taken as a whole at the time the present invention was made, it was not obvious to those of ordinary skill how the identified needs could be fulfilled.